Diffusion coefficients of the multicomponent beta-NiAl phase at 850, 950 and 1050 degrees C have been estimated as a function of composition by means of analyzing interdiffusion fluxes from concentration profiles which are obtained from the pack-aluminizing diffusion couples. The results indicate that values of D-AlNi(int) and D-Alco(int) are strongly composition dependent and values of D-AlCr(int) are slightly composition dependent. There exist significant differences in values of D-AlNi(int) between obtained in this study and reported in the literature for the binary NiAl phase. These differences become larger as the temperature decreases. This can be explained by the variation of the thermodynamic properties of the multicomponent beta-NiAl phase, which results from the solid solution of the alloying elements present in the nickel-based superalloy. The changes in the electronic structure due to the atomic size mismatch between the solute and solvent atoms may partially be responsible for these differences. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.